This is a proposal for partial support of participation of M.D. Anderson Hospital physicists in approved experiments at the Los Alamos Meson Physics Facility which satisfy some of the recommendations of the Subcommittee on Radiation Therapy of the LAMPF Biomedical Steering Committee. These experiments have been allocated an initial 150 hours of beam time and will be among the earliest experiments performed at LAMPF. The measurements will employ the Low Energy Pion Channel which should be in operation several months before the Biomedical Channel. Two basic experiments are planned. One experiment will be the measurement of the quality of meson radiation fields in order to determine the depth-dose, LET distribution and beam contamination resulting from the beam of negative pions. The relative abundance by number and by dose contribution of the pions and its associated muons, electrons, and neutrons must be determined to asses their relative impact upon clinical application. Essential data unto itself, it also will assist in forming the basics for comparison to future computer dosimetry calculations needed for therapy and to evaluation of beam transport designs. The other experiment will be an investigation of newly developed multi-wire proportional counters as potential tools for visualization of treatment volume. The techniques to be employed in these experiments all have been tested at the Space Radiation Effects Laboratory and were found to be satisfactory for the proposed studies. Improvements are presented in this proposal. As seen from the communication with LAMPF Beam Scheduling Committee, this first experiment (LAMPF Proposal #84) has been selected for first scheduling opportunities. The second experiment (LAMPF Proposal #83) has been approved by the Program Advisory Committee but not yet scheduled.